For an efficient operation of an internal-combustion engine running on gasoline or other liquid hydrocarbons it is necessary to insure a substantially complete gasification of the fuel which is drawn, in intimate admixture with atmospheric air, into the combustion cylinders of the engine for ignition therein. In many instances, especially with heavier hydrocarbons such as diesel oil, preheating of the fuel to a temperature near or above its boiling point has been found advantageous. It has also been proposed to use the waste heat of the engine for this purpose by letting the fuel pass in heat-exchanging relationship with the exhaust gases to the carburetor in which it is admixed with the air aspirated by the pistons of the engine.
Except in the case of diesel engines, in which the oil is injected at high temperature and pressure into the piston cylinders for spontaneous ignition therein, the use of medium-weight and heavy hydrocarbons in internal-combustion engines has up to now been rather limited despite the aforementioned teachings of the art. This, I believe, is mainly due to the difficulty of obtaining a thorough vaporization of these less volatile hydrocarbons. Thus, the usual boiling chambers heated by exhaust gases retain a significant proportion of the incoming fuel in liquid form on the chamber bottom, at least part of this liquid eventually finding its way into the lubricating system of the engine and being therefore lost to the power-generating process.